Telephone system



Feb. 1.1, E V|BBARD TELEPHONE SYSTEM Filed NOV. 17, 1954;

NMS Y ,//vl/ENTOR E.L.V/BBARD A T TORNEV Patented Feb. 11, 1936 UNITEDSTATES PATENT OFFICE TELEPHONE SYSTEM Application November 17, 1934,Serial No. 753,434

7 Claims.

This application relates to telephone systems and has for its objects tofacilitate the testing of the functioning of relays used in suchsystems.

Throughout the telephone system there are circuits which are maintainedover contacts of relays which, if opened by the failure of the relaycontacts, would cause the release of the connection involved or othermutilation of the operation.

Heretofore, such relay contacts have been tested by the use of otherrelays in which case poor adjustment of the relay under test is notdetected until it is bad enough to cause trouble in service. f

In accordance with the present invention,

1'5` means is provided for detecting poor relay contacts before theybecome bad enough to mutilate connections. More specifically, theinvention contemplates the inclusion of a gas-filled tube in a circuitincluding the contact to be tested,

2'0 ionizing the tube to complete the circuit, with means responsive tothe deionization of the tube to indicate failure of the contact.

The invention will be more clearly understood from a consideration ofone embodiment thereof l as shown in the attached drawing and set forthin the description which follows.

One case in which relays have been tested for their ability to remainoperated under adverse conditions is described in U. S. Patent No.

341,650,721 granted to R. E. Peoples on November 29, 1927 and, forconvenience, the present invention has been shown as it would beembodied in such a testing arrangement. A skeletonized showing has beenmade and the same reference characters employed as in the Peoplespatent.

Reference characters less than 100 apply to equipment added for thepresent disclosure.

The Peoples patent covers the routine testing of district selectors andfor that purpose picks the district selectors one at a time by means ofswitches which are indicated by brushes |924, |925, and 925. After theselector has been freed from the service link circuit, the test circuitYcauses the line nder, represented by brushes 2334 and 233|, to find thetest line appearing in the line nder frame in terminals 2333 and 2332.

The test circuit simulates the action of the sender in directing theselector brushes (not shown) to the test line which appears in thedistrict selector frame and then tests the supervisory relays, thecharging equipment, etc.

As soon as the line nder has found its test line,

a circuit is closed from battery through the winding of relay 402, backcontact of relay 403, conductor 494, upper front content of relay |4 I6,contacts of cam |6|3, brush- |925, conductors |949 and 2315, contact ofcam 2335, upper back contact of relay 23H, brush 2334, terminal 2333,conductor winding of relay H39, right front contact of relay |99,conductor 2936, terminal 2332, brush 233|, lower back contact of relay23H, winding of relay 2339, contact of cam 2329, conductors 2382 and|937, brush |924, conductor |2|8, contacts of cam |032, conductor |033,back Contact of relays |91, 52| and 49E), front contact of relay |223,winding of relay contact of cam |934 to ground. At the same time, acircuit is closed from battery through the lower winding of relay 23| l,contact of cam 23|6, conductors 23|5 and |938, brush |925, contact ofcam |25, conductor 24|, outer lower contact of relay MSS, conductor |4resistances 46 and 41 to ground at the contact of cam 93. This circuitcontains suflicient resistance to make a non-operate test of relay 23Hand the release of either relay |596 or 42 due to the opening of theback contacts of relay 23|'l would indicate serious lack of adjustmentof relay 23| l and would block the test.

In order to detect lack of adjustment in relay 23H while it is stillinsufficient to actually mutilate a call, a more severe test is made ofthe relay during the test of the district selector in connection with asimulated abandoned call which takes place with the test class sequenceswitch in position 8. When this sequence switch reaches position S, acircuit is closed from ground over cam 83 through the winding of relay425 to ground.

After the line inder has been positioned on the line finder test line,the test previously traced is made with sequence switch 999 in position2. Other tests are then made and sequence -switch 99 is advanced inresponse thereto to position l. When sequence switch 999 reachesposition 51/2 a circuit is closed from ground at the right contact ofrelay 425, right contact of cam 933 to the -L winding of relay 493 andbattery. Relay 493 locks to ground over cam 99 and transfers the testcircuit from the winding of relay 492 to the anode of the gas-filledtube 3. When sequence switch 959 reaches position l, ground from thefront contact of relay 429 is extended over the left Contact of cam 933to the winding of relay 4 and battery. Relay 4 connects ground toresistances 491 and 46 to complete the non-op'- erate circuit of relay23H.

I'he tube 3 is a gas-filled tube of the threeelectrode type in which anegative biasing potential on the control element or grid of the tubeholds the tube inert. A momentary reduction of this negative biasingpotential causes the tube to ionize and current to ilow from the cathodeto the anode, this current flow being independent of subsequent changesin the potential of the grid.

The grid of tube 3 normally receives its negative bias frompotentiometer 5. When relay 4 operates, it momentarily connects groundover its left following contacts to potentiometer 5, reducing thenegative bias on the grid of the tube long enough to cause the tube toflash and extend the test circuit through the tube between anode andcathode and through the Winding of relay 8 to battery. If the testcircuit is completed properly, relay 8 operates connecting ground to thetiming means which measures 01T a predetermined ti me interval.

At the end of this interval, if relay 8 is still operated, ground isextended from the timing means to the Winding of relay 6 and battery.Relay 6, in operating, closes a circuit for relay 490 which connectsground from the lower Contact ci cam 9il3, over the front contacts ofrelays 490 and 42S, through resistance 432 to the circuit of relay 23Hin parallel with resistance 401. This reduces the resistance in thiscircuit to the maximum through which relay 23I`I should operate. Ifrelay 23H is correctly adjusted it will operate, opening the testcircuit, quenching tube 3, releasing relays I and 8. Relay I, inreleasing, connects ground from cam I034, over the back contact of relayI, contact of cam 2 to the Winding of sequence switch 900 which advancesout of position 1, releasing relay 4 and initiating other tests of thedistrict selector Which are of not interest in this connection.

During the non-operate test of relay 23I'I, ground from the left frontcontact of relay 4 is connected to the left armature of relay I. Ifrelay I releases during the time interval measured by the timing means,it completes a circuit over its back contact and the back contact ofrelay 6 through lamp 'I to battery, lighting lamp 'I as an indicationthat relay 23H operated falsely on the non-operate test. When relay 6 isoperated at the end of the time interval, it connects the .left frontcontact of relay I over the right front contact of relay E to lamp 9 andbattery. Since relay il causes the closure of the operate circuit ofrelay 23H, the circuit of lamp 9 Would be ciosed for too short aninterval to permit it to light iully if relay 23II operates properly.

If relay 23H is not properly adjusted so that it attracts its armaturesin response to the noncperate current sufficient to break one of itsback contacts for as short an interval as .001 second, the tube 3 willquench and cannot be reionized except by the reoperation of the testcircuit, thus making it possible todetect much shorter openings of acircuit than was formerly the case.

It is, of course, understood that the present embodiment of theinvention is merely a typical use of the invention in the testing ofelectrical contacts.

What is claimed is:

1. In a telephone system, a contact to be tested, testing equipmentincluding a gas-filled tube having a cathode, an anode and a grid, meansto prepare a circuit including the contact to be tested, said cathodeand said anode, and means to ionize said tube to complete the testcircuit.

2. In a telephone system, a contact to be tested, testing equipmentincluding a gas-filled tube having a cathode, an anode and a grid, meansto prepare a circuit including the Contact to be tested, said cathodeand said anode, means to normally hold said grid at a potential toprevent the ionization of said tube, and means to momentarily vary thepotential on said grid toionize said tube t0 complete said testingcircuit.

3. In a telephone system, a contact to be tested, testing equipmentincluding a gas-lled tube having a cathode, an anode and a grid, meansto prepare a circuit including the contact to be tested, said cathodeand said anode, means to normally hold said grid at a potential toprevent the ionization of said tube, means to momentarily vary thepotential on said grid to ionize said tube to complete said testingcircuit, and means responsive to the deionization of said tube toindicate the failure of said contact.-

4. In a telephone system, a contact to be tested, testing equipmentincluding a gas-lled tube having a cathode, an anode and a grid, meansto prepare a circuit including the contact to be tested, said cathodeand said anode, means to normally hold said grid at a potential toprevent the ionization of said tube, means to momentarily vary thepotential on said grid to ionize said tube to complete said testcircuit, means responsive to the deionization of said tube to indicatethe failure of said contact, and means to prevent the reionization ofsaid tube following such deionization.

5. In a testing system, a relay to be tested, a gas-lled discharge tube,means for simultaneously establishing a non-operate circuit for saidrelay and for causing said tube to flash, and means to maintain theflashing circuit of said tube under the control of said relay.

6. In a testing system, a relay to be tested, a non-operate circuit forsaid relay, a gas-lled discharge tube including a cathode, an anode anda grid, a testing circuit including a test relay, a Contact of said rstrelay and the cathode and anode of said tube, means to normally maintainsaid grid at a potential to prevent the flow of current in said testingcircuit, means for momentarily grounding said grid to render said tubeconductive and means responsive to said test relay to indicate theresult of the test.

7. In a testing system, a relay to be tested, a non-operate circuit forsaid relay, a gas-filled discharge tube including a cathode, an anodeand a grid, a testing circuit including a test relay, a contact of saidiirst relay and the cathode and anode of said tube, means tonormally'maintain said grid at a potential to prevent the flow ofcurrent in said testing circuit, means for momentarily altering thepotential on said grid to render said tube conductive and meansresponsive to said test relay to indicate the result of the test.

EDWARD L. VIBBARD.

